I think the confusing issue is -- what is good chemistry in xenocrysts, how is it determined, and what statistics must the xenocrysts have with regard to that chemistry?
If a promoter says "great chemistry" or "we have G10's" I will grant you that the chances of economics are not assured. However good chemistry is more than G10's.
Yeah, that sure is one aspect of the issue. Another is, what exactly is a G-10? That is, by what definition. There is a difference,
Good chemistry is much more than G-10s in any case.
The factors that agur well statistically for pipe economics are: (these are biased towards non-eclogitic kimberlite)
1. pipe being in a regionally low geotherm (<40 mw heat radiation per sq metre).
Absolutely. Give me 35 mW/m^2 or less and I'm very excited.
OK. This is a long list, and rather than simply agree with most, I'll limit my comments to the ones I disagree with, or have something to add.
2. pipe being about ~50+ miles of craton/archon edge, or in euogeosyncline.
I'm curious about position relative to cratons, but I'm not able to make any definitive conclusions at this stage. You're not alone in the belief however.
3. large size of pipe.
Another interesting one, if you're suggesting the largest ones within a cluster have the best grades. There's some minor correlation between size and grade perhaps.
4. other economic pipes being in proximity
Big time. Absolutely. I'm a big fan of this one.
6. tendency for pipe to be crater or at least diatreme facies at surface.
Yes, in most circumstances. I used to firmly believe this, although I have wavered just a wee bit of late.
8. low oxygen fugacity of pipe (low diamond resorbtion on ascent).
Yes, among other indicators of low resorbtion.
9. tendency of pipe to form large diamonds.
Yes, if you're referring to the size distribution of the stones. The coarser the better. Of course, if you know that, you pretty much know the answer.
11. copious micro diamond content (rough indicator and lack thereof does not rule anything out).
No. Well, sort of. OK, yes, there is a positive correlation between micros and grade, but it's very misleading in many cases if you ignore the size distribution.
16. presence of huge macrocrysts.
I think so.
20. highly serpentinized olivine.
Hmmm. I haven't even tried this one.
22. high quality of diamonds found.
At what stage? Determining "quality" of micros is meaningless. If the quality at mini-bulk stage is good, you already know the answer. ;-)
That's a decent list.
The comments about uneconomic pipes are also good. Good luck testing an eclogitic deposit with mini-bulk samples.
Was there just one play that got misleading numbers by using X-Ray sortex only? I can think of two, I believe.
Regards,
WillP |
